explained | Will the US 5G guidelines have an impact on flights?

Can the expansion of 5G networks and aviation safely coexist? What did the FAA order?

The story so far: On December 7, 2021, the United States Federal Aviation Administration (FAA) issued two airworthiness directives (effective December 9, 2021) that are intended to create a framework and collect more information on the potential effects of 5G on aircraft. essential aviation safety equipment. . The FAA has also said it is working with the Federal Communications Commission and wireless companies to ensure that the expansion of 5G and aviation can safely coexist. The Federal Communications Commission is an independent US government agency overseen by Congress that regulates “interstate and international communications by radio, television, wire, satellite, and cable in the 50 states, the District of Columbia, and the US territories.” It is the leading authority on communications legislation, regulation and technological innovation.

Why is this important?

On November 2, 2021, the FAA issued a special airworthiness information bulletin containing “initial information on possible interference from 5G C-band wireless transmissions.” These steps are important as the American wireless communication companies are preparing at the beginning of January 2022 to start the transmission in “C-Band” (in 46 places), which is a range close to that used by certain aeronautical equipment. This will be in addition to the other frequencies already used for 5G.

What is the essence of the FAA guidelines?

In short, the directives concern two categories of air transport, the first being transport and shuttle class aircraft and the second, helicopters. . It is estimated that more than 6,800 aircraft equipped with radio altimeters will be affected; they include planes manufactured by Airbus, Boeing, Embraer and Gulfstream to name a few.

The guidelines address cellular 5G’s “potential radar altimeter interference threat” in the 3700 MHz-3800 MHz frequency, or C band – another report puts it at 3700-4200 MHz – which is close 4200 MHz-4400 MHz range used by aircraft radio altimeters, according to the FAA. The guidelines will also require highlights in the flight / flight operations manuals that will limit flight operations when such interference is encountered. Aircraft operations, including large jets, could be restricted or prohibited from using certain landing and navigation systems in locations where there is a possibility of potential interference with new 5G cellular networks. The restrictions could be severe for small planes and helicopters. Overall, this could lead to flight cancellations, delays or diversions at 46 locations where these towers are located, according to an aviation report.

A report indicates that telecommunications companies in the United States are expected to start activating additional 5G frequencies as early as January 5, 2022. In November 2021, these companies announced a voluntary restriction on the output power of cell phone towers (using these frequencies) in locations near an estimated 46 airports and other strategic locations for approximately six months. The FAA has also researched specific data on the location of 5G towers, their power supply, and angles to study how they may interfere with aircraft approaches. This could lead to what experts call “better, less disruptive warnings.”

What equipment on the plane can be affected?

An Airbus commander and senior examiner said The hindu that all medium and large commercial airplanes have two types of altimeters: barometric altimeter and radio altimeter. The barometric altimeter displays the aircraft’s altitude above mean sea level and uses ambient pressure to measure altitude. It is subject to various errors and requires certain corrections but has the advantage of giving altitude measurements up to the cruising level of the aircraft. It is used for all air traffic control reporting and separation and altitude maintenance purposes, as all aircraft can use a common specified data such as MSL or aerodrome altitude. . Most commercial airplanes have two radio altimeters, with the indication displayed on the main flight display. The antennas are placed in the fuselage of the aircraft.

The radio altimeter, he said, is a misnomer because it measures the height (not altitude) of the aircraft above the surface immediately below the aircraft. For this purpose, it transmits a radio signal directly below. While older systems calculated height based on the time elapsed between transmitting and receiving the reflected signal, more modern radio altimeters use more sophisticated techniques such as “measuring the phase shift of the reflected signal”. This is very accurate at close range. Most radio altimeters are limited to about 2,500 feet above surface level. In short, the radio altimeter gives the height above the immediate terrain. For all modern commercial aircraft, it is a very important tool used for precision approaches and landing. For example, on an Airbus, the radio altimeter input is used by the system to authenticate the aircraft’s glide path while performing an Instrument Landing System (ILS) approach. Thus, if the two radio altimeters are not available, the pilot would be forced to make a manual approach. There are various other systems that depend on the inputs of the radio altimeter – for example, the predictive wind shear, the ground proximity warning system, the road collision avoidance system and the automatic landing, he said. declared. These effects only occur when the aircraft is close to the ground, that is, up to 2,500 feet above the ground (depending on the make of the aircraft). The non-availability of the radio altimeter can be crucial during approach and landing for most modern aircraft and any disturbance of the internal readings of the radio altimeter caused by 5G or other equipment transmitting in close frequency bands can have consequences. disastrous effects on critical systems during approach. /landing.

Another senior commander who flies Boeing planes said the problem can grow as the radio altimeter is essential for any kind of precision approach which is almost 100% used at large airports these days. There is concern that the working frequencies of 5G and the radio altimeter are relatively close to each other, he said.

What are the lessons of the guidelines?

According to Captain A. (Mohan) Ranganathan, a former airline trainer pilot and aviation safety advisor, the FAA order has four important points.

The first is: “Prohibited operations include instrument landing system (ILS) approaches, required navigation performance (RNP) operations, automatic landing operations, and some use of vision vision systems. improved flight and other flight control systems ”. Captain Ranganathan says that if ILS, RNP and Autoland operations are prohibited, all operations fall under what is called a non-precision approach category that will require increased visibility and crossing limit requirements. ‘obstacles. For airports and passengers, this will translate into additional flight times and also more fuel requirements for each flight as the separation between flights will increase which will have a domino effect on flight delays. The effect could be worsened in areas that experience adverse weather conditions.

The second: The FAA’s separate helicopter order also prohibits automated flight that requires the use of radio altimeter data in areas affected by 5G. These operations include automatic hover. This means that helicopter flight in all areas near a town or city will become impossible unless they revert to manual flights.

The third: There is a warning of potential interference from both 5G base station transmissions and passenger cell phones. This is the greatest danger, he says, because the majority of passengers do not turn off cell phones. It could present an extreme danger when flying near major airports. Even though 5G tours are prohibited within a certain radius, any passenger who turns on and uses the phone (5G) while the aircraft is at lower altitudes and hovering due to delays, may be in danger.

The fourth: for large commercial aircraft, the risk is limited to “specific scenarios”, but can lead to “extreme” consequences in certain circumstances, such as when planes carry out instrument approaches in reduced visibility, specifies the directive. Approaches with reduced visibility, he said, represent a great danger because the aircraft is close to the ground and false entry into the autopilot system due to erroneous signals can lead to a crash.

Strict rules and criteria for punishment are needed to ensure safety, said Captain Ranganathan The Hindu.

Is there a problem with using the cell phone?

In 2000, Swiss aviation investigators believed that “electrical interference from a cell phone” may have been a factor in the crash of a small plane, Crossair flight LX 498, shortly after takeoff. A report says tests have shown that the small plane’s navigation system could be disturbed by signals from cell phones.

Earlier this year, the French Civil Aviation Authority warned that the latest generation of smartphones, 5G, could interfere with aircraft altitude instruments, and recommended that they be turned off during flight.

But so far, there has been no evidence that a cell phone has caused a crash.

What about the implications for India?

The Directorate General of Civil Aviation (DGAC) did not respond to an e-mail from The hindu for his comments.

A senior Boeing commander said Indian pilots are aware of the implications of 5G in the country, adding that there has been no official communication on the matter so far. In India, 5G could be deployed in the 3.2 GHz-3.6 GHz band, which may not have the potential to interfere with flight operations, according to an expert.

What is the way forward?

The Airbus commander-in-chief said there needs to be a lot more research to understand the full implications of 5G on the radio altimeter and other aircraft systems. Engineers could eventually figure out that this poses no serious threat. There could also be costly protective countermeasures or mitigation procedures. But until then, staying away from 5G seems like the easiest and safest option.

An aviation expert said wireless operators could also operate on certain C-band frequencies, leaving what is called a buffer between 5G signals and frequencies used in aviation.

And, Captain Ranganathan said that in India, the DGCA should order a ban on 5G towers within 15 nautical miles of any airfield with precision approaches such as ILS. With densely built up areas in many upcoming cities or near airports, interference with navigation signals can be catastrophic.

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